Field of the Invention
The present invention relates to a display device.
Discussion of the Related Art
In general, liquid crystal displays operate using the optical anisotropy and polarization properties of a liquid crystal. The molecules of the liquid crystal have an orientational order because of the long and thin structure of the liquid crystal, and the orientation of the molecules can be controlled by artificially applying an electric field to the liquid crystal. As such, arbitrary control of the orientation of the molecules in the liquid crystal can change the molecular arrangement of the liquid crystal, and a ray of light is refracted in the direction of orientation of the liquid-crystal molecules because of optical anisotropy, thus representing picture information.
Currently, active-matrix liquid crystal displays (AM-LCD; hereinafter, abbreviated as liquid crystal displays), in which thin-film transistors and pixel electrodes connected to the thin-film transistors are arranged in a matrix, are drawing the most attention because of their high resolution and video rendering capability. This type of liquid crystal display comprises a color filter substrate with a common electrode, an array substrate with pixel electrodes, and a liquid crystal sandwiched between the two substrates. In such a liquid crystal display, the common electrode and the pixel electrodes drive pixels by a vertically applied electric field, offering high transmittance and high aperture ratio. However, driving the liquid crystal by a vertically applied electric field has a poor viewing angle. To overcome this shortcoming, in-plane switching liquid crystal displays for a greater viewing angle were suggested. The in-plane switching liquid crystal displays have a wider viewing angle because the pixels are driven using a horizontal electric field between the pixel electrodes and the common electrode.
Along with the recent increase in display resolution, pixels per inch (PPI) are also increasing, leading to the current trend toward to smaller pixel size and pitch.
FIG. 1 is a plan view showing pixels and color filters in a display device according to a related art. Referring to FIG. 1, a red color filter CR, a green color filter CG, and a blue color filter CB are arranged to correspond to a red subpixel R, a green subpixel G, and a blue subpixel B, respectively. The size and pitch of subpixels are getting smaller due to the higher resolution. The subpixels require a pitch of approximately 3 μm in order to allow the patterning of the color filters. Thus, if the pitch of the subpixels is decreased to less than approximately 2.2 μm due to the higher resolution, this makes it difficult to make the color filters. Also, the color filters require a width of approximately 10 μm in order to allow the patterning of the color filters. However, if the width of the subpixels is decreased due to the higher resolution and the width of the color filters is decreased to less than approximately 8.4 μm, this also makes it difficult to make the color filters. If the width of opening regions in the subpixels is decreased to less than 4.4 μm, the opening regions in the subpixels will are narrow due to the black matrix. Because the black matrix will have a linear width of only 4 μm.
With the reduction in the size and pitch of the subpixels due to the higher resolution, the size and width of the color filters to be provided on the color filter substrate of the display device need to be reduced, and the pitch of the black matrix needs to be reduced also. However, there are difficulties in forming a fine pattern because of the characteristics of the color filters and black matrix, making it difficult to cope with the higher resolution.